Control system



July 16, 1929. Q PR|NE 1,721,410

CONTROL SYS'IZEM Filed Dec. 18. 1925 Inventor": David C.Pfince,

His Attorney.

Patented July 16, 1929.

UNITED STATES 1,721,410 PAT T FF E-v nnvm c. .rnmcn, or .scnEnEctrAnY,new YORK, ASSIGNOR T GENERAL ELECTRIC comrnrrr, a CORPORATION or newroan.

CONTROL SYSTEM.

vApplication filed. December 18, 1925. Serial No. 76,332.

M invention relates to control systems, and has for its principal objecttheprovlsion of an improved system for controlling the transmissionofcurrent through an electronv discharge device such as a mercury arcrectifier connected between load and supply cir- 'cuits. v, 7 r

It is 'customary' to interconnect an alternating current supply circuitand a load circuit through means comprising a transformer and a mercuryrectifier and to connect equalizing transformers between the rectifieranode leads having the same polarity for the purpose of ensuring theproper '15 distribution of current between these anodes.

When a mercury rectifier is utilized to transmit current between'anialternating current.

supply circuit and a load circuit connected to an electrical locomotiveor the like, it is desirable both to limit the number of maintransformer taps. used to step" up and step down the voltage of the loadcircuit and to effect these steps in the load circuit voltage withoutinterrupting the load circuit connections. In accordance with myinvention, these results are produced by correlating changes in the mainand equalizing trans-- former connections in a manner to maintain theload circuit connections while the load circuit voltage is "changed by aseries of steps which greatly exceed the number of main transformer tapsthrough-which these steps in voltage are produced.

My invention will be better understoodfrom the following descriptionwhen considered in connection with the accompany ing drawing and itsscope will be. pointed out in. the appended claims,

,The drawing shows a control system wherein my invention has beenembodied;

This system comprises a machine 1 to which currentis supplied from analter nating current circuit 2 through a transformer windin 3 groundedat a point intermediate its en s, a control device 4, and .a mercuryrectifier 5 which comprises anodes 6,7,8 and 9 and-acathode'lO. Thecontrol device 4 comprises stationary contact members 11 to 32 andmovable con-. tact members'33 to 38. The movable contacts are mounted ona rotatable drum or the like which may be operated to move the'contact33 sucessively into 'engagementwith the com tacts 14, 13, 12 and 11, thecontact 34 successively into engagementiwith the contacts "Thecontroller 4 is-operablepto difi'eren't 'po- 18, 17 16 and 15,'thecontact 35 successively into engagement with the contacts 22, 21, 20 and19, the contact'36 successively into engagement with the contacts 26,25, 24 and 23, the contact 37 successively into engagement with thecontacts 29, 28 and 27, and the contact 38 successively into engagementwith the contacts 32, 31 and 30. i

The main transformer secondary winding 3 1s grounded at the center andits upper and lower'portions are provided, with taps 39 to 42 and 43 to.46 respectively. It will be observed that the taps 39, 40, 41, 42, 43,44, 45, and 46 are respectively connected to pans of stationary segments14 and 18, 13 and 17, 12 and 1 6, 11 and 15, 22 and 26, 21 and 25, 20and 24, and 19 and 23. The contacts 33 and 34 are connected to anodes6., and 7 through the. windings 47 and 48 of an equalizing transformer.49. The movable contacts 35 and 36' are likewise connected to anodes 8and 9 through the windings 50 and 51 of an equalizing transformer 52.The

movable contacts 37 and38 aretconnected to the lower terminals of theequalizing transfor mer windings 47. and 50 respectively and the upperterminals of these' windings are respectlvely connected to groups ofstationary contacts 27,28 and 29 and 30, 31 and '32.-

sitions which 'are indicated by'the letters A, B, C, D, E,:F,- G and .ItWill'be readily understood that thelpotentials of the transformer taps,39, 40, 41- and 42 .are equal in value andtipposedin phase-to thepotentials of the tags 43, 44, 45 and 46; respectively.

With t e controller in the position A," the circuit between the maintransformer and the rectifier is interrupted and no current is suppliedto the load circuit to which the motor 1 is connected. Movement of thecontroller .to the position B causes a voltage corresponding to thetransformer taps 39 and 43 to be applied to the load circuit. When thecontroller is moved to the position 100 (Lathe anodes 7 and 9are'connected to the lowest voltage taps of the main transformer winding3 while the anodes 6 and 8 are con nected to' the next to the lowestvoltage taps of this winding. Under these conditions, the 105 anodes 6and 8, which are operating at a higher voltage than the anodes 7 and 9,tend to carry all the current transmitted through the rectifier andwould transmit all this our- "rent but for the fact that the equalizing1 10 cuiting of the equalizing transformer windings 47 and 50 due toengagement of contacts 37 and 38 with contacts 29 and 32 respectively,thus causing the arcs of the rectifier to be transferred to the anodes 6and 8 and raising the load circuit voltage to" a value corresponding tothe second voltage tap of the main transformer. The second step resultsin the connection of the anodes corresponding to the next highestvoltage transformer taps is thus made by raising the 7 and 9 to the samerespective transformer taps as the anodes 6 and 8 due to engagement ofcontacts 34and36 with the segments 17 and 25 respectively. The thirdstep results in removal'of the short circuits from 'the equalizingtransformer windings 47 and 50 due to disengagement of the contacts 37an anodes at a voltage which still corresponds to the second tap of themain transformer winding 3. i I

Transfer fromthe voltage corresponding to-the low voltage transformertaps to that voltage of anodes 6 and 8, equalizing the currents betweenthe anodes 6 and 7 and between the anodes 8 and 9 to produce a volt agebetween that corresponding to the first and second voltage taps of themain transformer, short circuiting windings 47 and 50 of the equalizingtransformers to cause the voltage at which current is transmittedthrough the rectifier to be raised to a value corresponding to thesecond transformer tap, changing the connections of the anodes 7 and 9to the second transformer tap while current is carried by the anodes 6andf8 at a voltagecorresponding to the second taps, and removing theshort circuits from the equalizing transformer windings to cause currentto be equally divided between the anodes 6, 7, 8 and 9 at a voltagecorresponding to thesecond taps. Additional steps in raising the loadcircuit voltageare per formed in the manner just describtL and will bere adily understood without further explanation. I

It will be apparent that for each succeeding transformer tap .voltage atleast two different voltages will be applied to the load circuit. Thismethod of operation therefore has the great advantage that the number ofvoltage steps is increased without correspondingly increasing the numberof main transformer taps and Without inter- 38 from the segments 29 and32, thus causing current to be equalized between the rupting theconnections of the load circuit.

The embodiment of the invention illustrated and described herein-hasbeen selected .for the purpose of clearly setting forth the principlesinvolved. It will be apparent, however, that the invention issusceptible of beingjmodified to meet the dif ferent conditionsencountered in its use and I thereforeaim to cover by the appendedclaims all modifications within the true spirit and scope of myinvention.

\Vhat I claim as new and desire to secure by Letters Patent of theUnited States is:

1. The method .of controlling a circuit supplied with current through amercury vapor arc device wherein anodesv of like- 'polar1ty arelnterconnected through an equalizing transformer, which comprisesapplying different voltages tof said anodes, equalizing the currents ofsaid anodes for applying to said circuit a voltagejintermediate saidvoltages, and short circuiting a,

winding of said equalizing transformer to raise the vbltage of saidcircuit to a value corresponding to the higher of said voltages.

2. The method of controlling a circuit supplied with current through amercury vapor arc device wherein anodes of like polarity areinterconnected. through an equalizing transformer, which comprisesapplying different voltages to said anodes, equalizing the currents ofsaid anodes for applying to said circuit a voltage intermediate saidvolta es,

short circuiting a windin of said equa izing transformer-to ralse t evoltage of said circuit to a value corresponding to the higher of saidvoltages, applying the higher of said voltages to all of said anodes,and removing the short circuit from said winding to equalize thecurrents of said-anodes.

3 The method of controlling a circuit supplied with current through amercury vapor arc device wherein anodes of like polarity.

are interconnected through an equalizin transformer which comprisesapplying di ferent voltages to said anodes, equalizing the currents'ofsaid anodes for applying to said circuit a voltage intermediate saidvoltages,

short circuiting a winding of said equalizing transformer to change thevoltage of said circult to a value corresponding to one of saidvoltages, applying said voltage to all of said anodes, and removing theshort circuit from said winding to equalize the cur'rents of saidanodes.

4. The combination of a mercury vapor arc device comprising'a cathodeand a plurality of anodes mounted within an evacuated chamber, currentsupply means for simultaneously applying voltages of the same polarityto a group of said anodes, means for interconnecting said device andsaid supply means to simultaneously apply different voltages todifferent anodes of said group, and means for equalizing the currents ofthe anodes of said group for producing between said cathode and anodes avoltage having a value intermediate said values of said differentvoltages.

5. The combination of a mercury vapor arc device comprising a cathodeand a plurality of anodes, current supply means for simultaneouslyapplying voltages of the same polarity to a group of said anodes,

1 means for equalizing the currents of the anodes of said group, and asingle control the voltage between said cathode and anodes to a valuecorresponding to the higher of said voltages.

In witness Whereof I have hereunto set my hand this 17th day ofDecember, 1925.

DAVID PRINCE.

